Looks like my house as well 
I'd second what flow4 says about the possibility of damp in the parts that are back to earth. We had to have the walls and floor of our ground floor removed and re-tanked at huge expense when we moved in to our house due to the river which flowed through the living room in the Autumn! Also, when we couldn't take the leaks in the roof any more, the scaffolding alone cost more than most houses' new roofs cost
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WRT Grade two listing, check what exactly is listed about the house. If it's windows (as I suspect it may be), and they will soon need replacing, that could be very expensive. In fact, whatever bit of the house is listed, have it checked over by a builder you trust and if repairs will soon be needed, use the cost to negotiate on the price.
The stairs are a bit of a pain when I'm knackered, but DH is a willing fetcher and carrier. When we needed stair gates they cost a fortune (we had to buy 7 to cover all the different stair-casey bits in the house, and they were all unusual sizes), but now the babies are 6.7 and 9, and they're all whizzing up and down without any problems, although I regularly lose a child or two, due to all the different levels and rooms
I'd say, if you love it, you'll be able to live with the shortcomings, so take the plunge!